The phototransduction event in Aplysia neurons is being investigated. The nature of the ions carrying the current across the plasma membrane are being identified. The transmitter substance released internally is thought to be calcium. The amount of calcium and photopigment in the lipochondria granules which are the source of both and are contained in the cytoplasm are being measured quantitatively. The lipochondria granules have been isolated and the effects of light on calcium release and uptake are being investigated. BIBLIOGRAPHIC REFERENCES: Brown, A.M., M.S. Brodwick and D.C. Eaton. 1977. Intracellular calcium and extraretinal photoreception in Aplysia giant neurons. J. Neurobiol. 8: 1-18. Baur, P.S., A.M. Brown, T.D. Rogers and M.E. Brower. 1977. Lipochondria and the light response of Aplysia giant neurons. J. Neurobiol. 8: 19-42.